Secondary structure and NMR resonance assignments of the C-terminal DNA-binding domain of Uup protein

ATP-binding cassette (ABC) systems belong to a large superfamily of proteins that couple the energy released from ATP hydrolysis to a wide variety of cellular processes, including not only transport of various molecules, but also gene regulation, and DNA repair. Mutations in the bacterial uup gene, which encodes a cytosolic ABC ATPase, lead to an increase in the frequency of precise excision of transposons Tn10 and Tn5, suggesting a role of the Uup protein in DNA metabolism. Uup is a 72?kDa polypeptide which comprises two ABC domains, separated by a 75-residue linker, and a C-terminal domain (CTD) of unknown function. The Uup protein from Escherichia coli has been shown to bind DNA in vitro, and the CTD domain contributes to the DNA-binding affinity. We have produced and purified uniformly labeled ¹⁵N- and ¹⁵N/¹³C Uup CTD domain (region 528?C635), and assigned backbone and side-chains resonances using heteronuclear NMR spectroscopy. Secondary structure evaluation based on backbone chemical shifts is consistent with the presence of three ??-helices, including two long ones (residues 564?C590 and 601?C632), suggesting that Uup CTD may fold as an intramolecular coiled coil motif. This work provides the starting point towards determining the first atomic structure of a non-ATPase domain within the vast REG subfamily of ABC soluble ATPases.